A single large asteroid can hold as much platinum as has ever been mined on Earth, but the real value of these treasure troves might be in their less glamorous contents.

Hydrogen, oxygen or ammonia extracted from asteroids could be used to refuel spacecraft or provide radiation shielding for deep-space missions far beyond the asteroid belt. "The idea is to set these [asteroids] up as gas stations, and grow the economy in space so that we no longer need to carry up everything out of Earth's gravity well," says Ian Webster, the creator of Asterank, a database that charts over 600,000 asteroids.

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Efforts are under way to claim this prize. Asteroid mining startup Planetary Resources secured $21 million (£15.7m) in funding in May to build a satellite system to monitor the use of the Earth's resources. Another US company, Deep Space Industries, is partnering with Luxembourg's government to launch a test asteroid prospector in 2017.

One spacecraft is looking for samples already. In December 2014, Japan Aerospace Exploration Agency (JAXA) sent the spacecraft Hayabusa 2 to land on the asteroid Ryugu. If everything goes to plan, in 2020 it will return to Earth with samples from the asteroid which is worth $95 billion (£71bn), according to Webster's estimate. WIRED assesses the most lucrative mining destinations in space.